Ball valves are well known. One design that has met with substantial commercial success is the 60 Series ball valve manufactured and sold by Swagelok Company and are described in U.S. Pat. No. 4,410,165 (hereinafter the “'165 patent”) and U.S. Pat. No. 4,602,762, the entire disclosures of which are fully incorporated herein by reference. This ball valve design is characterized by a number of features that improve the seal performance and cycle life of the valve. The valve includes a pair of seat assemblies each on an opposite side of the ball member. Each seat assembly includes a flexible seat ring, a support ring and a disc spring. The disc spring urges the seat ring into sealing engagement with an outer surface of the ball, and the support ring reduces inward axial displacement and deforming of the seat ring when the valve is under pressure. A significant feature of the ball valve is that the ball and seats are “floating” so that the ball can shift axially under pressure. The floating ball design avoids the need for trunnion style mounting or other costly alternatives.
Other ball valve designs are shown in U.S. Pat. Nos. 6,695,285 and 5,163,655.